Movement Speed and Accuracy in Space and Time: The Complementarity of Error Distributions

Movement speed-accuracy trade-off is a function of the space-time constraints of the task. We investigated the space-time account of Hancock and Newell (1985) and the hypothesis of complementarity between the four moments of the error distribution in space and time. Twelve participants performed 15 conditions in a line drawing task composed of different spatial (10, 20, and 30 cm) and temporal (250 to 2,500 ms) criteria. The results showed that all moments of distributions changed systematically between conditions but there were some departures from the Hancock and Newell predictions. In contrast, individual analysis revealed the complementarity of the spatial and temporal error including a trade-off between the four moments of error. These findings support a complementary space-time account of movement speed and accuracy.     

Perceptual Learning of Tooling Affordances of a Jointed Object via Dynamic Touch

We investigated whether perceptual learning via dynamic touch can facilitate the discovery of tooling affordances. Twelve blindfolded participants manipulated two structurally identical aluminum objects consisting of a blade and a shaft; one object was seven and a half times heavier than and twice as large as the other object. Flexions/extensions at two joints in the shaft changed the configuration and functionality of each object. A rigid shaft (one of four possible configurations) rendered each object a functional hoe. The number of changes in the configuration produced prior to determining that the grasped object had been rendered a functional hoe greatly exceeded the number of possible configurations and declined with experience, whereas the rate of change in configuration increased with experience. Inertial properties specifically support perception via dynamic touch and explained the observed differences in actions with the two objects. These findings demonstrate that perceptual learning via dynamic touch can facilitate the discovery of tooling affordances.     

Spontaneous object recognition in capuchin monkeys: assessing the effects of sex,familiarization phase and retention delay

Animal Cognition - The spontaneous object recognition (SOR) task is a versatile and widely used memory test that was only recently established in nonhuman primates (marmosets). Here, we extended...     

What is special about indexical attitudes?

In this paper, I assess whether indexical attitudes, e.g. beliefs and desires, have any special properties or present any special challenge to theories of propositional attitudes. I being by investigating the claim that allegedly problematic indexical cases are just instances of the familiar phenomenon of referential opacity. Regardless of endorsing that claim, I provide an argument to the effect that indexical attitudes do have a special property. My argument relies on the fact that one cannot account for what is it to share someone else’s indexical attitudes without rejecting some plausible thesis about propositional attitudes. In the end, I assess Herman Cappelen and Josh Dever’s considerations on intentional action and extract an argument from them that could – if successful – neutralize my own. I finish by arguing that their argument has an important flaw, thus failing to convince us that indexical attitudes are just as ordinary as any other.     

Controlling Relations in Baseline Conditional Discriminations as Determinants of Stimulus Equivalence

The Psychological Record - Variation in baseline controlling relations is suggested as one of the factors determining variability in stimulus equivalence outcomes. This study used single-comparison...     

Search Strategies in Practice: Movement Variability Affords Perception of Task Dynamics

Practice has been conceptualized in terms of a search process through an evolving perceptual-motor workspace. The experiment was set up to examine whether the inherent variability of the system would influence perception of the relevant properties of the task space. We reanalyzed the data from Hsieh, Liu, Mayer-Kress, and Newell (2013) in which participants performed a speed-accuracy aiming task and feedback emphasized either temporal or spatial accuracy in different conditions. The maximum variability in spatial error during practice differentiated individual's best performance in the fast speed-accuracy conditions. Additionally, we found that a threshold of variability predicted discontinuities during practice within individuals. The findings support the proposition that inherent variability affords perception of the relevant dimension of the task. The search motion through the perceptual-motor workspace was continuous or discontinuous depending on the constraints of the movement speed-accuracy condition.     

Search Strategies in Practice: Testing the Effect of Inherent Variability on Search Patterns

Abstract

To execute a motor solution to a given task, individuals search through the space of movement possibilities guided by information that arises from the interaction with task and environment. Through this search, individuals seek to avoid inappropriate solutions through local minima in the task space. The processes that lead to some but not all individuals avoiding local minima and finding solutions is not yet understood. Based on the tenets of ecological psychology for perception and action, we examined in two experiments the hypothesis that the incapacity to differentiate errors (performance of an inappropriate solution) from inherent variability would interfere with the perception of properties of the task space and result in a longer time performing an inappropriate solution for the task before exploration of other solutions. Inherent variability was shown to be a direct predictor of the changes in the search strategies. Also, we found that the specifics of the search patterns could predict the performance in the task. Thus, the pattern of motion through the task space affords perception of specific properties of this space guiding individuals in the evolving dynamics of exploration or exploitation.